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16 Sep 2014, 00:12
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It takes computer A 6 hours and 40 minutes to finish a job. If computer B can process the same job in 10 hours, how long will it take, for both computers working together, to finish the job?
A. 6 hours and 20 minutes
B. 5 hours and 10 minutes
C. 4 hours and 40 minutes
D. 4 hours
E. 3 hours and 20 minutes
A. 6 hours and 20 minutes
B. 5 hours and 10 minutes
C. 4 hours and 40 minutes
D. 4 hours
E. 3 hours and 20 minutes
16 Sep 2014, 00:12
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Official Solution:
It takes computer A 6 hours and 40 minutes to finish a job. If computer B can process the same job in 10 hours, how long will it take, for both computers working together, to finish the job?
A. 6 hours and 20 minutes
B. 5 hours and 10 minutes
C. 4 hours and 40 minutes
D. 4 hours
E. 3 hours and 20 minutes
To finish the job, computer A takes 6 hours and 40 minutes, which equals \(\frac{20}{3}\) hours. So Computer A's rate is \(\frac{3}{20}\) of the job per hour.
Computer B's rate is \(\frac{1}{10}\) of the job per hour.
Their combined rate is: \(\frac{3}{20} + \frac{1}{10} = \frac{3}{20} + \frac{2}{20} = \frac{5}{20} = \frac{1}{4}\) of the job per hour.
Hence, it takes \(\frac{1}{\frac{1}{4} } = 4\) hours for both computers working together to finish the job.
Answer: D
It takes computer A 6 hours and 40 minutes to finish a job. If computer B can process the same job in 10 hours, how long will it take, for both computers working together, to finish the job?
A. 6 hours and 20 minutes
B. 5 hours and 10 minutes
C. 4 hours and 40 minutes
D. 4 hours
E. 3 hours and 20 minutes
To finish the job, computer A takes 6 hours and 40 minutes, which equals \(\frac{20}{3}\) hours. So Computer A's rate is \(\frac{3}{20}\) of the job per hour.
Computer B's rate is \(\frac{1}{10}\) of the job per hour.
Their combined rate is: \(\frac{3}{20} + \frac{1}{10} = \frac{3}{20} + \frac{2}{20} = \frac{5}{20} = \frac{1}{4}\) of the job per hour.
Hence, it takes \(\frac{1}{\frac{1}{4} } = 4\) hours for both computers working together to finish the job.
Answer: D
30 Dec 2021, 23:38
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I think this is a high-quality question and I agree with explanation.
